Production of uranium-carbon alloys



United States Patent Ofiice Patented June 9, 1964 The invention relates to the production of dense uranium-carbon alloys.

It is known from United States Patent No. 2,569,225 and British Patents Nos. 825,041 and 821,287 to produce uranium-carbon alloys containing varying proportions of uranium carbides and of differing structures, from mixtures of uranium and carbon. A preferred method of producing such alloys is to heat a cold-compacted mixture of uranium and carbon powders to a temperature of 800 to 1125 C. to cause a solid-state reaction between the uranium and carbon. Alloys produced by this method, however, have a density only about 9093% of theoretical and an open" porosity of 1 to 1 /2%.

According to the present invention a method of producing a dense uranium-carbon alloy, which may also comprise plutonium, comprises cold-compacting and then sintering at a temperature of at least 800 C., a mixture of uranium powder and carbon powder (and if desired plutonium powder) containing also iron in the form of an intermetallic compound of iron and uranium, the iron constituting from 1 to of the whole by Weight. The intermetallic compound may be UFeor U Fe, use of the latter being limited to iron contents less than 3.8% of the whole by weight. The preferred intermetallic compound is UFe since we have found that it gives the highest alloy density. The amounts of UFe corresponding to 1% and 10% by weight of iron are 3.1% and 31% respectively. The amount of U Fe corresponding to 1% by weight of iron is 26.5%; We have found that maximum density is attained when the iron content of the mixture is about 3% by Weight of the whole. This is achieved, for example, when the amount of UFe used is about 10% by Weight of the whole.

The uranium-carbon alloys which can be produced according to this invention may also include plutonium which may replace part of the uranium powder in the starting mixture.

We have found further, that when UFe is used as the intermetallic compound, the maximum density as a percentage of the theoretical density, and'also the minimum open porosity, is attained when the carbon content of the mixture is in the stoichiometric proportion to the uncombined uranium content to form uranium monocarbide, i.e., 4.8% by weight of the total of uncombined uranium and carbon.

Heating of the cold compacted mixture to effect the sin tering thereof must be performed at a temperature in excess of 800 C., which is the known temperature at which a solid state reaction takes place between uranium and carbon. However, the heating of the cold compacted mixture is preferably achieved very rapidly in accordance with the teachings set forth in our copending US. patent application Serial No. 53,634, filed September 2, 1960. As set forth in the aforesaid application, the cold compacted mixture of uranium powder, carbon powder, and intermetallic compound of iron and uranium is heated to a sintering temperature by plunging the mixture into a furnace heated to a temperature of 1000 C. to 1125 C. whereby the heat of reaction of the mixture sintering furnace causes its temperature to rise above the melting point of uranium. We have found that the rate of rise of temperature of the compacted mixture when it is plunged into the furnace is very rapid and depends upon British standard test sieve was mixed with ultrafine the size of the compact. It is certainly greater than 100 C. per minute, and may be as high as 500 C. per minute for small compacts. The actual temperature reached by the compact depends upon the size of the compact, but is within the range 1200 to 1450 C.

The nature of the invention will be made more apparent by the following examples.

EXAMPLES I TO VI Uranium powder of particle size to pass a 300 mesh and UFe were then cold-compacted at 60 tons/ sq. in. in

a tungsten carbide-lined die to form compacts of various sizes. Each compact was placed in an alumina boat and passed rapidly into a vacuum furnace heated to 1100 C.

Each compact was estimated to reach a maximum tem-' perature of 1200" to 1450 C. within a few minutes due to the heat of reaction, and was then heated at 1100 C. for 2 hours. The densities and porosities of the products are given in the following table, in which a product containing no UFe but" produced by the same method is included for comparison.

Table I Weight Density Porosity percent of whole (gin/cc.) (percent) Example UN; 0 Fe Theo Meas- Total Open retieal ured Table I shows that for lJFe contents between 5 and 30% 0 (iron contents 1.57 -to 9.40%) the density is substantially higher thanthe density when no UFe is used, and that the highest density and lowest total porosity is achieved when the UFe content is 10%. Furthermore the openv and 5.0% respectively.' The results obtained are shown in the following table:

Table H Weight Density Porosity percent of whole (gm./cc.) (percent) Example UFe 0 Fe Theo- Meas- Total Open retical ured Table II shows similar results to those of Table I.

EXAMPLES XIII-XVIII Similar mixtures to those of Examples 11 and VIII were cold-pressed and sintered as before, except that the pro- 5.4% The results obtained are shown in the following table: V

' Table III 7 Weight percent Density (gm./cc.) Porosity I carbon'- (percent) Example of [1/0 of whole Theore- Measured Total Open mixture tical 4. 3. 60 14. 13. 26 6. s 0.80 4. 2 3. 18 14. O0 13. 5. 4' O. 62 4. 4 3. 96 13. 86 13. 18 4. 9 O. 43 4. 6 4. 14 v13. 73 13. 12 4. 4' 0. 4. 8 4. 32 13. 59 13. 09 3.-7 0. 3 5. O 4. 50 13. 43 12. 87 .4. 4 O. 7 5. 2 4. 68 V 13. 28 12. 62, 5. U- i '1. 3 4. S6 ..13.16 12. 38 5. 9 l. 6

I containing-excess uram'umie. the. products of Examples XIII'to XVI, the interstices'containsa composition inter:

mediate between U and UFe- V In those containing excess carbonic. the products of'Ex'amples VII to} XII, XVII and XVIIII, the interstices contain a composition which consists of carbon and UFe which may react to form further HQ and free iron. 1

EXAMPLE XIX I A mixture of cold compacting the mixture, passing the mixture to a, sintering zone, heating such zone to a temperature ofbetween about 800 C. and 1125 C., and maintaining the mixture in such zone for a period of timesuflicient to elfect the complete sinterin g'thereof. V a 2. A method for producing .a uranium-carbon' alloy. of 'high density and Y low porosity comprising mixing uranium powder, carbon powder, anr iron inthe form of I an intermetallic compound of iron a'nd ur anium, the iron constituting'from about 1- to 10% of the Whole by'weight, cold compacting the mixture, passing'the compacted'rnixture to a sintering zone maintained at the time of passing of, the mixture at a temperature within. the range. *of;

V about 1000-1125 C., permitting the. temperature in thejf a period of time sufficientto effect a complete. sinteringof sinterling zone to rapidly, rise fora short period ofqtime V solely as a result of the exothermic heat generated by the f reaction of the mixture at a rate greater than about C.-per minute to a temperature between 'abouty1200-Q '-1450 C.,"and thereafter heating the 'mixturein said sintering zone at atemperature of about 1000-1-125 C. for

the mixture.

- ;A method according to claim 2, which thejiron V a I I constitutes'about 3% of-thewholeby weight.

' -4. 'A' method according to claim 2,;in' which the'iron 1 constitutes less than-3.8%" of the whole'by weightand ofthe'whole by weight.-

' i i 6.- A method according to claim 5 74. 2%. uranium powder and 25.8%

graphite'was mixed with U' Fe powder in an amount such i that the U Fe constituted 83.3% of the whole byweight- In this composition the iron content of the mixturewas i 3.13% and the carbon content 4.32%, as in-Example II.

The composition was cold-compressed and 's intered as the interstices between the UC particles; 7 e y We claimz,

comprises'about 10%"of the whole by weight. I V p I 7. A method according to claim 2 in which the *'uraniurn' 'carbon powden'and'iron.

9. A'formed uraniumcarb onfalloy of high densityjthe said 'intermetallic compound is UgFe comprising "at least 26.5%.. of the whole by weight. n o 5. A method according to claim 2, in which thesaid intermet'allic compound is UFeg comprising 3.1% to 31% .iniwhich use,

powderand "carbon; powder in thesaid mixture are in; the

stoichiometric proportionto form uranium monocarbide. i

8. A method in accordance with claim 2, wherein phi-' V toniumimetal powder is mixed and low. porosity consisting-essentiallyof an intimate sintered.mixturelofailraniummonocarbide particles with the! metallic compound of iron and uranium, the iron (3011-.

stituting .from about 1 10 10% of the whole by weight;

- before. The product had adensity-of only 12.20 gm.'/ cc.,' ii p a' in intfirstices betwfien the paftiles; I

but was of similar constitution to that of ExampleILie 1 V h ortion of iron insaid alloy. being between about 1 1? i uranium monocarbide; in intimate mixture with: UFe i to 10% byweightfl v I Q R eferences-Citedin' the me. drthi fp telii V A q UNIIEDr STATES PATENTS 2,526,805

- Carter with theJuranium powder,

Oct. 24, "1950" Sept. .5, 1951 Sept."24, 195.7'1 

1. A METHOD OF PRODUCING A URANIUM-CARBON ALLOY OF HIGH DENSITY AND LOW POROSITY COMPRISING MIXING URANIUM POWDER, CARBON POWDER, AND IRON IN THE FORM OF AN INTERMETALLIC COMPOUND OF IRON AND URANIUM, THE IRON CONSTITUTING FROM ABOUT 1 TO 10% OF THE WHOLE BY WEIGHT, COLD COMPACTING THE MIXTURE, PASSING THE MIXTURE TO A SINTERING ZONE, HEATING SUCH ZONE TO A TEMPERATURE OF BETWEEN ABOUT 800*C. AND 1125*C., AND MAINTAINING THE MIXTURE IN SUCH ZONE FOR A PERIOF OF TIME SUFFICIENT TO EFFECT THE COMPLETE SINTERING THEREOF. 